1. Field of the Invention
The present invention relates an input device for use in inputting operations for various types of electronic apparatuses, an electronic apparatus, and a method for controlling an input device.
2. Description of the Related Art
There have been a large number of commercial push-button type input devices, as input devices for use in inputting operations for electronic apparatuses such as cellular phones.
However, in recent years, along with advancing size reduction of such apparatuses, it has become increasingly difficult to secure spaces for installing such input devices.
In view of the circumstances, there have been suggested, for example, electronic apparatuses including sensors which sense change of capacitances due to fingers touching thereon and perform inputting and also including sheet-type EL (Electroluminescence) devices capable of light emission which are placed on the sensors, in order to improve viewability of its operation portions and to realize thickness reduction (refer to, for example, Japanese Patent Unexamined Publication No. 2005-346402).
The structure of such a conventional electronic apparatus will be described. FIG. 7 is a cross-sectional view for describing the structure of the conventional electronic apparatus.
Referring to FIG. 7, electronic apparatus 100 includes cabinet 101 and also includes, as an input device, sensor 102 and light emitting device 103 as an EL element, which are placed within cabinet 101 such that they are overlaid on each other. In this example, light emitting device 103 is provided on the front surface of cabinet 101, while sensor 102 is placed on the back surface of light emitting device 103.
Sensor 102 is a capacitive type sensor capable of detecting finger 104 of a user touching thereon, with cabinet 101 and light emitting device 103 interposed therebetween. In the case of employing such a capacitive type sensor, when finger 104 approaches the operation surface, a part of electric charge accumulated in sensor 102 is fed to finger 104, resulting in reduction of a capacitance value. The capacitive type sensor can detect finger 104 touching thereon, by detecting the change of the capacitance value.
Sensor 102 has a thin sheet shape and is mounted to light emitting device 103 with an adhesive material or the like.
The EL element used as light emitting device 103 has a thin sheet shape and is mounted to the back surface of cabinet 101 with an adhesive material or the like. In this example, the EL element is configured to emit light when a luminescent substance therein is excited by an electric field and is capable of emitting uniform light over a wide range.
As described above, conventional electronic apparatus 100 can be made thinner in comparison with electronic apparatuses including push-button type input devices and also is capable of emitting light from light emitting device 103 during operations, thereby improving viewability of its operation portion.
However, conventional electronic apparatus 100 has a problem of noises generated when the EL element as light emitting device 103 is driven, wherein such noises may influence the capacitive type sensor, thereby preventing it from detecting fingers touching thereon and positions with high accuracy.